1. Technical Field
The present invention relates to the processing of video signals, and more particularly, to the conversion of interlaced video formats into progressive video formats known as deinterlacing.
2. Description of the Related Art
Presently, many of the transmitted and broadcast TV signals are interlaced. Many of these signals are transmitted in Moving Picture Experts Group (MPEG) form. For example, the Advanced Television Systems Committee (ATSC) has developed the standard for digital television wherein the signals, referred to as ATSC signals, are transmitted in MPEG form. Some of the ATSC formats are interlaced, for example 480i and 1080i video signals. These MPEG signals are in the so-called 4:2:0 format. Accordingly, the MPEG signals contain chroma, the difference signal portion of the video signal, of half-spatial resolution in both horizontal and vertical directions. In order to display this chroma with the associated luma, the matrixed red, green, and blue portion of the video signal, the chroma must be converted back to 4:4:4 form.
Most MPEG decoders output the chroma component after it has been formatted to match the interlaced luma output. Typically, such MPEG decoders will convert the interlaced 4:2:0 chroma into interlaced 4:2:2 chroma. If the resulting chroma and luma are to be deinterlaced and possibly converted to a different number of lines, the chroma vertical resolution will be degraded if the usual chroma output of the decoder is deinterlaced.
Many new displays, such as plasma, LCD, LCOS, and other “matrix” type displays, are being developed which are inherently progressive, or non-interlaced. Accordingly, in addition to decoding, converting the video signal to 4:2:2 format, and then deinterlacing the video signal, to properly display a video signal on many inherently progressive displays, the video signal must undergo further vertical format conversion. This can result in further degradation of the chroma vertical resolution. For example, in the case where a 1080i signal is to be displayed on a 720p display, most MPEG decoders will convert the 270 lines per field of 4:2:0 chroma to 540 lines per field by vertical interpolation. Typically, both the chroma and luma components of the signal would be deinterlaced producing a 1080p signal. This sequence degrades the vertical resolution. Moreover, the down-conversion of the luma from 1080 to 720 lines, and up-conversion of the chroma from 540 to 720 lines, can further degrade the vertical resolution. The present invention is directed towards reducing this degradation.